Several experiments are planned in continuing work on two neural peptides, substance P and neurotensin that have been isolated, sequenced and synthesized in this laboratory. The studies include: a) mapping the distribution of these peptides in peripheral nerve and autonomic ganglia, b) the chemical characterization of substance P and neurotensin in plasma, c) efforts to manipulate the levels of immunoreactive substance P and neurotensin in plasma by various stimuli, d) measuring the effect of different dietary regimens on the intestinal content of immunoreactive neurotensin, e) an investigation of the effect of substance P and neurotensin on LH secretion in prepubertal female rats. Recently the interesting finding has been made that a cell line from a transplantable WAG/Rij rat medullary thyroid carcinoma synthesis and secretes both calcitonin and neurotensin. This may provide an excellent system in which to study agents that regulate the secretion of neurotensin.